Electrically alterable read only memory (EAROM) semiconductors are used as programmable non-volatile memory devices. Such memory devices in the form of individual memory cells can be laid down as part of an integrated circuit chip (IC) in predetermined patterns with high density at a relatively low cost. Such devices require low power and are relatively simple to erase and write by applying appropriate voltages to the gate electrode of the device. They have found widespread use in a variety of devices, for example, radio and television tuners, program storage circuits, etc.